The present invention relates to an image forming apparatus including a density detection means for detecting a reflection density of a patch toner image formed in the image carrier so that the density of a formed image can be stabilized.
In an electrophotographic image forming apparatus, in order to prevent the deviation of density of a formed image, image density is detected from the reflection density data of an image that has been fixed. The efficiency of the above image forming apparatus is not high from the viewpoint of conserving natural resources because transfer sheets are used for the detection of image density, and further the image productivity is not so high. In order to solve the above problems, there is provided an image forming apparatus in which the deviation of image density is prevented in the following manner. A patch toner image is formed on the image carrier, and then the formed toner image is made to be visual. Using the visual patch toner image, while consideration is given to a difference between the image density on the image carrier and the image density on a transfer sheet, the image density is calculated. In this way, the deviation of image density of the formed image can be prevented.
As one of the image forming apparatus in which image density is detected as described above, there is provided an apparatus in which a plurality of gradation correction curves are prepared and the most appropriate gradation correction curve is selected in accordance with the detected image density. However, the number of the gradation correction curves stored in the apparatus is limited. Therefore, it is impossible to conduct an accurate gradation correction.